High-performance nanogenerators based on flexible cellulose nanofibril/MoS2 nanosheet composite piezoelectric films for energy harvesting

Highlights: • TOCN/MoS₂ nanocomposite films exhibit excellent piezoelectric property (d₃₃=31 pC/N). • TOCN/MoS₂ nanocomposite films do not contain the heavy metals present in traditional piezoelectric materials. • The mechanical strength of the TOCN/MoS₂ nanocomposite film is extremely good. • The flexible TOCN/MoS₂ PENG can be used for efficient energy harvesting. High-performance and environment-friendly biomass-based piezoelectric films have drawn much attention recently. Here, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibril (TOCN)/molybdenum disulfide (MoS₂) nanosheet bionanocomposite piezoelectric films were prepared through an environmentally benign pathway by aqueous dispersion. The TOCN/MoS₂ nanocomposite films exhibited good mechanical properties with the highest Young's modulus of 8.2 GPa and tensile strength of 307 MPa. When the MoS₂ content was 4 wt%, the longitudinal piezoelectric constant (d₃₃) of the composite film reached a maximum value of 31 pC/N, much higher than 12 pC/N of the neat TOCN film and other reported cellulose-based piezoelectric films. Moreover, nanogenerators fabricated from TOCN/MoS₂ composite films exhibited a maximum output voltage of 4.1 V and a short-circuit current of 0.21 μA. Furthermore, the current generated by the nanogenerator was rectified and converted to direct current. A 10 μF commercial capacitor was charged to 1.6 V at 120 s, indicating the ability to collect mechanical energy generated in the natural environment. Therefore, the TOCN/MoS₂ composite films are promising in the field of piezoelectric materials and nanogenerators.